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Nitrogen Recycling and Remobilization Are Differentially Controlled by Leaf Senescence and Development Stage in Arabidopsis under Low Nitrogen Nutrition
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Edité par CCSD ; Oxford University Press ; American Society of Plant Biologists -
International audience. Five recombinant inbred lines (RILs) of Arabidopsis (Arabidopsis thaliana), previously selected from the Bay-0X Shahdara RIL population on the basis of differential leaf senescence phenotypes ( from early senescing to late senescing) when cultivated under nitrogen ( N)- limiting conditions, were analyzed to monitor metabolic markers related to N assimilation and N remobilization pathways. In each RIL, a decrease of total N, free amino acid, and soluble protein contents with leaf aging was observed. In parallel, the expression of markers for N remobilization such as cytosolic glutamine synthetase, glutamate dehydrogenase, and CND41- like protease was increased. This increase occurred earlier and more rapidly in early-senescing lines than in late-senescing lines. We measured the partitioning of (15) N between sink and source leaves during the vegetative stage of development using (15) N tracing and showed that N remobilization from the source leaves to the sink leaves was more efficient in the early-senescing lines. The N remobilization rate was correlated with leaf senescence severity at the vegetative stage. Experiments of (15) N tracing at the reproductive stage showed, however, that the rate of N remobilization from the rosettes to the flowering organs and to the seeds was similar in early- and late-senescing lines. At the reproductive stage, N remobilization efficiency did not depend on senescence phenotypes but was related to the ratio between the biomasses of the sink and the source organs.
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